Might catch the Connemara Allblacks Rugby in Clifden, Ennis is big on GAA so see some Irish sport Hurling or Football (not Soccer!) But it would depend on days with most sports taking place on weekends although there may be some midweek events.

As to off the beaten track? Depends on interests??

But assuming Dublin figures on top of the list of places you have a lot in there for 12 days anyway.

Off the beaten path:

Sligo: Gleniff Horseshoe Drive
Donegl: Glengesh Pass, Slieve League cliffs, Rossnowlagh beach
Clifden: Sky Drive, Dog's Bay (near Roundstone)
Killarney: Everything here is pretty much on the map - perhaps driving the interior of the Ring of Kerry
Kinsale: James Fort (across the river from Charles Fort up the hill behind The Dock Pub)
Ennis: Clare Abbey

Tony, we fly into Shannon July 28 / spend one night in Ballyfarnon / spend two nights in Donegal City / spend two nights in Clifden / spend two nights in Killarney National Park / spend two nights in Kinsale / spend last night in Ennis.

Clifden to Westport via the N59 and returning back down between Clew Bay and Croagh Patrick then the Doolough valley is a regular day trip we do when over in Clifden. You could head for the pilgrimage if you must but it wouldn't be the day I would choose to climb the Reek. I wouldn't say avoid at all costs but there's a lot of folk and not much road if you get my meaning.